Control valve for variable displacement compressor

ABSTRACT

To provide a control valve for a variable displacement compressor, which is simple in construction and excellent in controllability. Between a port for introducing refrigerant at discharge pressure Pd 1  delivered from a discharge chamber and a port for allowing refrigerant at discharge pressure Pd 2  to flow out at a controlled flow rate, there are provided a main valve the valve lift of which is varied according to the flow rate of refrigerant passing therethrough, and a solenoid valve that uses a valve element of the main valve as a variable valve seat and supplies to the crankcase the refrigerant at pressure Pc the flow rate of which is controlled according to the size of a gap formed between the variable valve seat and the hollow cylindrical valve element. The main valve not only senses the flow rate but also serves as the valve seat of the solenoid valve, and the solenoid valve controls the small flow rate of refrigerant supplied to the crankcase. Therefore, the control valve is simple in construction, and capable of performing stable flow rate control.

CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY

This application claims priority of Japanese Application No. 2004-162122 filed on May 31, 2004 and entitled “CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR” and No. 2004-196230 filed on Jul. 2, 2004, entitled “CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a control valve for a variable displacement compressor, and more particularly to a control valve for a variable displacement compressor, which is mounted in the compressor and capable of providing control such that a flow rate of refrigerant discharged therefrom becomes constant.

(2) Description of the Related Art

A compressor used in a refrigeration cycle of an automotive air conditioner, for compressing refrigerant, uses an engine as a drive source, and hence is incapable of performing rotational speed control. To eliminate the inconvenience, a variable displacement compressor capable of varying refrigerant capacity (the discharge amount of refrigerant) is employed so as to obtain an adequate cooling capacity without being constrained by the rotational speed of the engine.

In such a variable displacement compressor, a wobble plate (swash plate) fitted on a shaft driven by the engine for rotation has pistons connected thereto, and is rotated within a crankcase while varying the inclination angle thereof, whereby the stroke of the pistons is varied to vary the capacity of the compressor, i.e. the discharge amount of refrigerant.

To change the inclination angle of the wobble plate, part of compressed refrigerant is introduced into the hermetically closed crankcase to cause a change in the pressure in the crankcase, whereby the balance of pressures acting on the opposite sides of each piston connected to the wobble plate is changed to continuously change the inclination angle of the wobble plate.

The pressure in the crankcase is changed by a control valve for a variable displacement compressor, which is disposed between the discharge port of refrigerant and the crankcase or between the crankcase and the suction port of refrigerant. This control valve provides control such that communication is allowed or blocked so as to maintain the differential pressure thereacross at a predetermined value, and more particularly, the differential pressure can be set to the predetermined value by externally changing a value of control current supplied to the control valve. With this configuration, when the rotational speed of the engine rises, the pressure introduced into the crankcase is increased to reduce the volume of refrigerant that can be compressed, whereas when the rotational speed of the engine lowers, the pressure introduced into the crankcase is reduced to increase the volume of refrigerant that can be compressed, whereby the amount of refrigerant discharged from the compressor is maintained constant.

One known method of controlling the capacity of such a variable displacement compressor uses a control valve therefor, which provides control such that the flow rate of refrigerant discharged from the compressor becomes constant (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2004-116349).

This control valve for a variable displacement compressor includes a variable orifice which is capable of changing the passage area of a refrigerant passage through which flows the refrigerant discharged from the compressor, using a solenoid by an external signal supplied thereto, and controls the flow rate of refrigerant introduced from the discharge chamber into the crankcase such that the differential pressure across the variable orifice becomes equal to a predetermined value. By holding the differential pressure across the variable orifice set to a certain flow passage area, at the predetermined value, the flow rate of refrigerant passing through the variable orifice is controlled to be constant.

However, the conventional control valve for a variable displacement compressor is configured such that it includes a first control valve that varies the flow passage area of the refrigerant passage, a solenoid section that sets the flow passage area according to a change in external conditions, and a second control valve that senses the differential pressure occurring across the first control valve and controls the pressure in the crankcase such that the differential pressure becomes equal to the predetermined value, and the first control valve through which high-pressure refrigerant is allowed to pass is controlled by the solenoid section to thereby directly change the flow passage area. Therefore, this control valve suffers from the problems that it is not easy to change the large flow passage area by the solenoid section, and the overall construction thereof is complicated.

SUMMARY OF THE INVENTION

The present invention has been made in view of these problems, and an object thereof is to provide a control valve for a variable displacement compressor, which is simple in construction and excellent in controllability.

To solve the above problem, the present invention provides a control valve for a variable displacement compressor, for providing control such that a flow rate of refrigerant discharged from the compressor becomes constant, comprising a main valve that is set to a first valve lift a lift amount of which is dependent on a flow rate of refrigerant passing therethrough which is discharged from a discharge chamber of the compressor, and a solenoid valve that is set to a second valve lift by an external signal, and controls a flow rate of refrigerant to be allowed to flow from the discharge chamber to a crankcase according to an amount of change in the first valve lift relative to the second valve lift set thereto.

The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conceptual configuration of a variable displacement compressor.

FIG. 2 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a first embodiment of the present invention, in a state during deenergization.

FIG. 3 is a cross-sectional view showing details of the control valve according to the first embodiment, in a balanced state during energization.

FIG. 4 is a cross-sectional view showing details of a control valve according to a second embodiment, in a balanced state during energization.

FIG. 5 is a cross-sectional view showing details of a control valve according to a third embodiment, in a balanced state during energization.

FIG. 6 is a cross-sectional view showing details of a control valve according to a fourth embodiment, in a balanced state during energization.

FIG. 7 is a cross-sectional view showing details of a control valve according to a fifth embodiment, in a balanced state during energization.

FIG. 8 is a cross-sectional view showing details of a control valve according to a sixth embodiment, in a balanced state during energization.

FIG. 9 is a cross-sectional view showing details of a control valve according to a seventh embodiment, in a balanced state during energization.

FIG. 10 is a cross-sectional view showing details of a control valve according to an eighth embodiment, in a balanced state during energization.

FIGS. 11A, 11B are views showing a main valve of the control valve according to the eighth embodiment, wherein FIG. 11A is side view of the main valve, and FIG. 11B is a cross-sectional view taken on line A-A of FIG. 11A.

FIG. 12 is a diagram showing changes in the flow rate of refrigerant occurring in response to electric current supplied to the solenoid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, embodiments of the present invention will be described in detail with reference to the drawings showing control valves applied to a variable displacement compressor of a fixed flow rate control type in which the flow rate of discharged refrigerant is controlled to be constant, by way of example.

FIG. 1 is a cross-sectional view of a conceptual configuration of a variable displacement compressor.

The variable displacement compressor includes a hermetically formed crankcase 1, which contain a rotating shaft 2 rotatably supported therein. One end of the rotating shaft 2 extends via a sealed bearing device to the outside of the crankcase 1, and a pulley 3 having a drive force transmitted from an engine for an automotive vehicle is fixed to the one end of the rotating shaft 2. The rotating shaft 2 has a wobble plate 4 fitted thereon such that the inclination angle of the wobble plate 4 can be varied. Around the axis of the rotating shaft 2, there are arranged a plurality of cylinders 5 (one of which is shown in FIG. 1). Each cylinder 5 has a piston 6 disposed therein, for converting the rotating motion of the wobble plate 4 into reciprocating motion. The cylinder 5 is connected to a suction chamber 9 and a discharge chamber 10 via a suction relief valve 7 and a discharge relieve valve 8, respectively. A control valve 11 for a variable displacement compressor is provided between the discharge chamber 10 and an outlet port formed to communicate therewith and between the discharge chamber 10 and the crankcase 1, and an orifice 12 is provided between the crankcase 1 and the suction chamber 9.

In the variable displacement compressor, the outlet port formed to communicate with the discharge chamber 10 is connected via a high-pressure refrigerant conduit line to a condenser 13, from which piping extends to the inlet port formed to communicate with the suction chamber 9 via an expansion valve 14, an evaporator 15, and a low-pressure refrigerant conduit line, whereby a refrigeration cycle as a closed circuit is formed.

In the variable displacement compressor constructed as above, as the rotating shaft 2 to which the drive force is transmitted from the engine is rotated, the wobble plate 4 fitted on the rotating shaft 2 wobbles while rotating. Then, each piston 6 connected to the outer peripheral part of the wobble plate 4 performs reciprocating motion in a direction parallel to the axis of the rotating shaft 2, whereby refrigerant at suction pressure Ps in the suction chamber 9 is drawn into the associated cylinder 5 and compressed therein, and the compressed refrigerant at discharge pressure Pd1 is discharged into the discharge chamber 10. At this time, high-pressure refrigerant in the discharge chamber 10 is decompressed to discharge pressure Pd2 when passing through the control valve 11, and delivered from the outlet port to the condenser 13. Part of the high-pressure refrigerant is introduced into the crankcase 1 via the control valve 11. This causes the pressure Pc in the crankcase 1 to rise, whereby the inclination angle of the wobble plate 4 is set such that the bottom dead center of the piston 6 is brought to a position where the pressure in the cylinder 5 and the pressure Pc in the crankcase 1 are balanced. Thereafter, the refrigerant introduced into the crankcase 1 is returned to the suction chamber 9 via the orifice 12.

The control valve 11 detects a flow rate of refrigerant sent from the discharge chamber 10 to the condenser 13, and introduces the refrigerant into the crankcase 1 at a flow rate dependent on the detected flow rate, thereby providing control such that the flow rate of the refrigerant sent from the discharge chamber 10 to the condenser 13 becomes constant. More specifically, when the rotational speed of the engine increases, the suction pressure Ps lowers, and the discharge pressure Pd1 rises. If this increases the flow rate of refrigerant sent from the discharge chamber 10 to the condenser 13 via the control valve 11, the flow rate of refrigerant introduced into the crankcase 1 is also increased, whereby the pressure Pc in the crankcase 1 increases. Accordingly, in the variable displacement compressor, the wobble plate 4 is inclined in such a direction as will cause the wobble plate 4 becomes at right angles to the rotating shaft 2 to decrease the stroke of the pistons 6, which acts on the compression capacity of the cylinders 5 in a reducing direction to reduce the discharge flow rate of refrigerant. Thus, even when the flow rate of discharged refrigerant is about to increase due to an increase in the rotational speed of the engine, the control valve 11 increases the flow rate of refrigerant introduced into the crankcase 1 according to the increase in the flow rate of refrigerant, whereby the pressure Pc in the crankcase 1 is increased to reduce the discharge capacity. Therefore, the flow rate of refrigerant discharged from the compressor is controlled to be constant.

Inversely, when the rotational speed of the engine lowers, the flow rate of refrigerant sent from the discharge chamber 10 to the condenser 13 via the control valve 11 is decreased, whereby the flow rate of refrigerant introduced into the crankcase 1 is also decreased to lower the pressure Pc in the crankcase 1. As a result, the discharge flow rate of refrigerant is increased whereby the flow rate of discharged refrigerant is controlled to be constant.

Now, a description will be given of examples of the construction of the control valve for a variable displacement compressor.

FIG. 2 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a first embodiment of the present invention, in a state during non-energization. FIG. 3 is a cross-sectional view showing details of the control valve according to the first embodiment, in a balanced state during energization.

The control valve 11 has a main valve 20 and a solenoid valve 21 actuated by solenoid, which are accommodated in a body 22. The body 22 is formed with three ports 23, 24, and 25. When the control valve 11 is mounted in the variable displacement compressor, the port 23 is communicated with the discharge chamber 10 to introduce refrigerant at discharge pressure Pd1. The port 24 is communicated with the outlet port of the compressor to deliver refrigerant at discharge pressure Pd2. The port 25 is communicated with the crankcase 1 to deliver refrigerant at the controlled pressure Pc.

The body 22 has an upper portion thereof, as viewed in FIG. 2, formed with a refrigerant passage 26 extending therethrough to communicate between the port 23 and the port 24, and in the refrigerant passage 26, a valve seat 27 of the main valve 20 is formed integrally with the body 22. On a downstream side of the valve seat 27, a valve element 28 is disposed in a manner opposed to the valve seat 27 such that the valve element 28 is movable to and away from the valve seat 27. This valve element 28 has a through hole extending therethrough along the axis of the body 22, and a piston 30 hanging from a holder 29 capped on an upper end of the body 22, as viewed in FIG. 2, is inserted in the through hole, whereby the piston 30 holds the valve element 28 in a manner movable axially back and forth. Between the valve element 28 and the holder 29, the spring 31 is interposed to urge the valve element 28 in a valve-closing direction, whereby the main valve 20 has a check valve structure.

The solenoid valve 21 uses the valve element 28 of the main valve 20 as a movable valve seat, and has a hollow cylindrical valve element 32 that can be inserted in and removed from a valve hole defined by the through hole formed in the valve element 28 and forms a slide valve in cooperation with the movable valve seat provided by the valve element 28. The valve lift of the hollow cylindrical valve element 32 is controlled by solenoid. The hollow cylindrical valve element 32 is held in the body 22 in a manner movable axially back and forth.

The solenoid has a bottomed sleeve 33 having an open end thereof hermetically fixed to the body 22, and a core 34 is fitted in the opening of the bottomed sleeve 33. The core 34 has a through hole formed therethrough for having the hollow cylindrical valve element 32 loosely fitted therein along the axis thereof. A plunger 35 is disposed within the bottomed sleeve 33 in a manner movable to and away from the core 34, and is urged by a spring 36 in a direction away from the core 34. Fitted in the plunger 35 is a lower end of the hollow cylindrical valve element 32, as viewed in FIG. 2, which is held by the body 22. A coil 37 is circumferentially provided outside the bottomed sleeve 33, and surrounded by a yoke 38 integrally formed with the body 22. The yoke 38 has an annular plate 39 fitted in a lower end thereof, as viewed in FIG. 2, between the yoke 38 and the plunger 35, for forming a magnetic circuit.

The hollow cylindrical valve element 32 is provided with a hole 40 at a location corresponding to the port 25, whereby the port 23 through which refrigerant at discharge pressure Pd1 is introduced and the port 25 communicating with the crankcase 1 are communicated via a gap between the valve element 28 of the main valve 20 and the hollow cylindrical valve element 32 and a hollow part of the hollow cylindrical valve element 32. The hollow cylindrical valve element 32 is provided with a pressure-equalizing hole 41 in the vicinity of a portion thereof fitted in the plunger 35, for communication between the inside of the bottomed sleeve 33 and the port 25, to thereby cause the pressure Pc to equally act on the opposite ends of the hollow cylindrical valve element 32 in the direction of motion thereof, whereby the pressure Pc never influences the control operation of the solenoid 21.

In the control valve 11 constructed as above, as shown in FIG. 2, when the solenoid is not energized, the main valve 20 is fully closed by having the valve element 28 seated on the valve seat 27 by the spring 31, and the solenoid valve 21 is fully open since the plunger 35 is urged by the spring 36 in the direction away from the core 34, and the hollow cylindrical valve element 32 fixed to the plunger 35 is moved away from the valve element 28 as the variable valve seat associated therewith.

Therefore, in this state, when the drive force is transmitted from the engine to the rotating shaft 2 to cause rotation thereof, in the compressor, the wobble plate 4 provided on the rotating shaft 2 performs wobbling motion while rotating. The wobbling motion of the wobble plate 4 causes the reciprocating motion of the pistons 6 connected to the peripheral part of the wobble plate 4, whereby the refrigerant in the suction chamber 9 is drawn into the cylinder 5 to be compressed therein, and the compressed refrigerant is discharged into the discharge chamber 10. At this time, since the main valve 20 is in the fully closed state, the refrigerant discharged into the discharge chamber 10 passes through the solenoid valve 21 in the fully open state, and flows to the port 25 via the hollow part of the hollow cylindrical valve element 32 and the hole 40, to be introduced into the crankcase 1. This places the compressor in the minimum capacity operating state. The force of the spring 31 acting on the main valve 20 in the valve-closing direction is set to be somewhat larger than the force generated by the discharge pressure Pd1 in the valve-opening direction when the compressor is operating with the minimum capacity, and hence the closed state of the main valve 20 is maintained.

When predetermined control current is supplied to the coil 37 of the solenoid, the plunger 35 of the solenoid valve 21 is attracted to the core 34, and as shown in FIG. 3, the hollow cylindrical vale element 32 is lifted to a position where the attractive force of the solenoid and the urging force of the spring 36 are balanced, and stopped thereat. At this time, the valve element 28 of the main valve 20 still remains seated in the valve seat 27, as shown in FIG. 2, and hence the hollow cylindrical valve element 32 of the solenoid valve 21 is inserted into the valve hole formed in the valve element 28, whereby the solenoid valve 21 is momentarily fully closed. This prevents introduction of refrigerant into the crankcase 1, which causes prompt transition of the compressor to its maximum capacity operating state, to increase the discharge capacity Pd1 drastically. The discharge pressure Pd1 causes the valve element 28 of the main valve 20 to be lifted against the urging force of the spring 31, whereby the valve element 28 of the main valve 20 is lifted to a lift amount dependent on the flow rate of refrigerant. At this time, the hollow cylindrical valve element 32 of the solenoid valve 21 is removed from the valve hole formed in the valve element 28 to open the solenoid valve 21, whereby the refrigerant is allowed to flow through a gap between the hollow cylindrical valve element 32 and the valve element 28 into the crankcase 1 at a flow rate dependent on the size of the offset between these, whereby the compressor performs transition to a state of operation with the predetermined capacity.

Here, if the rotational speed of the engine increases, the suction pressure Ps lowers, and the discharge pressure Pd1 rises. This increases the flow rate of refrigerant delivered from the discharge chamber 10, and accordingly, the valve element 28 of the main valve 20 is further lifted to increase the flow passage area of the main valve 20, which is about to cause an increase in the flow rate of refrigerant discharged from the compressor. The further lift of the valve element 28 increases the offset between the hollow cylindrical valve element 32 of the solenoid valve 21 and the valve element 28 as the movable valve seat associated therewith to increase the flow rate of refrigerant introduced into the crankcase 1 to thereby increase the pressure Pc in the crankcase 1. Therefore, the compressor acts in the direction of reducing its capacity, and is thus controlled such that the flow rate of discharged refrigerant is reduced.

Inversely, when the rotational speed of the engine lowers, the flow rate of refrigerant delivered from the discharge chamber 10 decreases to also reduce the flow rate of refrigerant introduced into the crankcase 1, whereby the pressure Pc in the crankcase 1 lowers, so that the compressor acts in the direction of increasing the discharge capacity.

Thus, the control valve 11 constantly acts such that it takes a balanced position as shown in FIG. 3, whereby even if the flow rate of refrigerant discharged from the compressor is about to change due to a change in the rotational speed of the engine, the compressor is controlled in the direction of decreasing the flow rate of refrigerant discharged from the compressor. As a result, the flow rate of refrigerant discharged from the compressor is controlled to be constant.

FIG. 4 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a second embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 4 identical or similar to those shown in FIGS. 2 and 3 are designated by identical reference numerals, and detailed description thereof is omitted.

The control valve 51 according to the second embodiment is distinguished from the control valve 11 according to the first embodiment in that the structure of the solenoid valve 21 is modified. More specifically, the solenoid valve 21 comprises a hollow cylindrical movable valve seat 52 held in a body 22 in a manner movable axially back and forth, and a hollow cylindrical valve element 54 having the same diameter as that of the hollow cylindrical movable valve seat 52, held on a guide 53 hanging from the holder 29 in a manner movable back and forth along the axis of the body 22, and at the same time, fixed to the valve element 28, and is configured such that the hollow cylindrical movable valve seat 52 is actuated by the shaft 55 fixed to the plunger 35. One end of the hollow cylindrical movable valve seat 52, which is opposed to the hollow cylindrical valve element 54, is expanded in a funnel-like fashion to form a valve seat face, and a hole 56 is formed at a location where the port 25 is formed, whereby a hollow part of the hollow cylindrical movable valve seat 52 is communicated with the port 25 communicating with the crankcase 1.

As to the main valve 20, the valve element 28 thereof is rigidly fitted on the hollow cylindrical valve element 54, and the hollow cylindrical valve element 54 is fitted in the guide 53, whereby the valve element 28 is held in a manner movable axially back and forth.

In this control valve 51 as well, when a predetermined control current is supplied to the coil 37 of the solenoid, the solenoid valve 21 is stopped at a point where the attractive force of the solenoid and the force of the spring 36 are balanced, whereby the hollow cylindrical movable valve seat 52 is set to a valve lift corresponding to a discharge flow rate as a target. This causes the main valve 20 to be lifted according to a flow rate of refrigerant discharged from the discharge chamber 10 of the compressor, and the flow rate is eventually controlled such that it is set to a flow rate of refrigerant set by the solenoid valve 21.

FIG. 5 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a third embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 5 identical or similar to those shown in FIGS. 2 and 3 are designated by identical reference numerals, and detailed description thereof is omitted.

The control valve 61 according to the third embodiment is distinguished from the control valve 11 according to the first embodiment in that the structure for holding the valve element 28 of the main valve 20 in a manner movable axially back and forth is modified and at the same time the pressure acting on the hollow cylindrical valve element is changed. More specifically, the core 34 of the solenoid is extended upward, as viewed in FIG. 5, to the location of the port 23 where the refrigerant at discharge pressure Pd1 is introduced, and a hollow cylindrical valve element 62 is held by the core 34 in a manner movable back and forth along the axis thereof. This hollow cylindrical valve element 62 has the plunger 35 of the solenoid fixed to a lower end thereof, as viewed in FIG. 5, and a plug 63 fitted in an upper end thereof, as viewed in FIG. 5, and is urged by the spring 64 downward, as viewed in FIG. 5.

The hollow cylindrical valve element 62 has the valve element 28 of the main valve 20 fitted thereon in the vicinity of the upper end thereof and the valve element 28 is movable back and forth using the hollow cylindrical valve element 62 as the guide along the axis thereof. The hollow cylindrical valve element 62 is provided with a hole 65 such that the hole 65 cooperates with the valve element 28 of the main valve 20 to form a valve portion of the solenoid valve 21, and is further provided with a hole 66 at a location where the port 25 is formed.

The core 34 of the solenoid is provided with a pressure-equalizing hole 67 in parallel with the hole for holding the hollow cylindrical valve element 62, such that the discharge pressure Pd1 is introduced into the bottomed sleeve 33 of the solenoid. With this configuration, the hollow cylindrical valve element 62 receives the discharge pressure Pd1 in an upward direction and the discharge pressure Pd2 in a downward direction, as viewed in FIG. 5. The differential pressure across the valve element 28 is very small compared with the discharge pressure Pd1, and hence substantially the same pressure acts on the opposite ends of the hollow cylindrical valve element 62 in the direction of motions thereof, which prevent the control operation of the solenoid valve 21 from being adversely affected.

Similarly to the control valves 11 and 51 according to the first and second embodiments, the control valve 61 also controls the compressor such that the flow rate of refrigerant delivered from the discharge chamber 10 becomes constant.

FIG. 6 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a fourth embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 6 identical or similar to those shown in FIG. 5 are designated by identical reference numerals, and detailed description thereof is omitted.

The control valve 71 according to the fourth embodiment is distinguished from the control valve 61 according to the third embodiment in that a part of the solenoid for driving its valve element is divided.

A hollow cylindrical valve element 72 supported on the core 34 has a plug 73 inserted in a portion of a hollow part thereof downward, as viewed in FIG. 6, of a location where the port 25 is formed, and fixed thereat, whereby the port 25 and the bottomed sleeve 33 are fluidically separated from each other. Disposed between the plug 73 and the plunger 35 is a shaft 74, and one end of the shaft 74 is in abutment with the plug 73, and the other end of the same is fitted in the plunger 35. This causes axial motion of the plunger 35 to be transmitted to the hollow cylindrical valve element 72 via the shaft 74 and the plug 73.

This control valve 71 as well controls the flow rate of refrigerant allowed to flow into the crankcase 1 according to the lift of the main valve 20, thereby controlling the compressor such that the discharge flow rate of refrigerant becomes constant.

FIG. 7 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a fifth embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 7 identical or similar to those shown in FIG. 6 are designated by identical reference numerals, and detailed description thereof is omitted.

As is distinct from the control valve 71 according to the fourth embodiment in which the pressure introduced into the solenoid is the discharge pressure Pd1 upstream of the valve element 20, in the control valve 81 according to the fifth embodiment, the pressure is set to the discharge pressure Pd2 downstream of the main valve 20.

To introduce the discharge pressure Pd2 into the bottomed sleeve 33 of the solenoid, the body 22 is provided with a pressure-equalizing hole 82, and the core 34 is provided with a pressure-equalizing hole 83 such that the pressure-equalizing hole 83 communicates with the pressure-equalizing hole 82. This causes the same discharge pressure Pd2 to act on the opposite ends of the hollow cylindrical valve element 72 in the directions of motion thereof, which prevents discharge pressure Pd2 from adversely affecting the control operation of the solenoid valve 21.

FIG. 8 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a sixth embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 8 identical or similar to those shown in FIG. 4 are designated by identical reference numerals, and detailed description thereof is omitted.

The control valve 91 according to the sixth embodiment is distinguished from the control valve 51 according to the second embodiment in that damper means is added to the main valve 20. More specifically, the valve element 20 has a valve element 92 having a cup shape, and the valve element 92 is held within a cylinder 93 recessed inside the holder 29 in a manner movable axially back and forth. The hollow cylindrical valve element 54 of the solenoid valve 21 fixed to the valve element 92 of the main valve 20 is also held within the guide 53 hanging from the holder 29 in a manner movable back and forth along the axis thereof. The upper opening of the holder 29 is closed by a plate 94, whereby a space defined between the inside of the valve element 92 of the main valve 20 and the outside of the hollow cylindrical valve element 54 of the solenoid valve 21, where the spring 31 is accommodated, forms an approximately hermetically closed chamber.

Now, when the discharge pressure Pd1 introduced into the port 23 is suddenly changed, the valve element 92 of the main valve 20 is about to be fluctuated due to a sudden change in the received pressure, but a progressive increase or decrease of the volume of the hermetically closed chamber absorbs the sudden change in the received pressure, whereby the valve element 92 is prevented from being suddenly fluctuated, whereby the vibrating noise generated by fluctuating motion of the valve element 92 can be reduced.

FIG. 9 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to a seventh embodiment of the present invention, in a balanced state during energization. It should be noted that component elements in FIG. 9 identical or similar to those shown in FIGS. 2 and 3 are designated by identical reference numerals, and detailed description thereof is omitted.

As is distinct from the control valve 11 according to the first embodiment in which the solenoid valve 21 is implemented by a slide valve, in the control valve 101 according to the seventh embodiment, the solenoid valve 21 is implemented by a poppet valve.

More specifically, in the control valve 101, the hollow cylindrical valve element 32 has a frustoconical valve element 95 fitted on the upper end thereof, as viewed in FIG. 9, thereby forming a valve portion of the solenoid valve 21. The valve element 95 has a through hole extending axially therethrough and having the same inner diameter as that of the hollow cylindrical valve element 32, and is capable of moving to and away from the rim of the through hole formed in the valve element 28 of the main valve 20 in a manner interlocked to the axial motion of the hollow cylindrical valve element 32. This causes the valve element 95 to be closely seated on the valve seat formed on the valve element 28 of the main valve 20, which makes it possible to reduce leakage of refrigerant from the solenoid valve 21.

FIG. 10 is a cross-sectional view showing details of a control valve for a variable displacement compressor, according to an eighth embodiment of the present invention, in a balanced state during energization, and FIGS. 11A and 11B are views showing a main valve of the control valve according to the eighth embodiment, wherein FIG. 11A is side view of the main valve, and FIG. 11B is a cross-sectional view taken on line A-A of FIG. 11A. FIG. 12 is a diagram showing changes in the flow rate of refrigerant occurring in response to electric current supplied to the solenoid. It should be noted that component elements in FIG. 10 identical or similar to those shown in FIG. 8 are designated by identical reference numerals, and detailed description thereof is omitted.

The control valve 111 according to the eighth embodiment is distinguished from the control valves 11, 51, 61, 71, 81, 91, and 101 according to the first to seventh embodiments, in that the structure of the main valve 20 is modified.

More specifically, the main valve 20 includes a valve element 112 that can be moved to and away from the valve seat 27 formed in the refrigerant passage 26, and the valve element 112 is integrally formed with a hollow cylindrical skirt 113 which is extended therefrom into a valve hole of the main valve 20 and is slidably disposed therein, and a hollow cylindrical portion 115 the lower end of which forms a valve seat 114 of the solenoid valve 21, which are arranged on the same axis. Inserted into the hollow cylindrical portion 115 is a guide 116 hanging from the holder 29. The solenoid valve 21 has a hollow cylindrical valve element 117 held in the body 22 in a manner axially movable to and from the valve seat 114, and the hollow cylindrical valve element 117 is provided with a valve hole 118 so as to cause the hollow part of the valve element 117 to communicate with the port 25. An upper end of the hollow cylindrical vale element 117 on a side opposed to the valve seat 114 is formed to have a frustoconical shape, and makes up a poppet valve in cooperation with the valve seat 114.

The valve element 112 of the main valve 20 is configured, as shown in FIG. 11, to have a tapered portion 119 such that the vale element 112 is closely seated on the valve seat 27, so as to maintain a sufficient closed state when the main valve 20 functions as a check valve. The skirt 113 formed integrally with the valve element 112 has at least one slit 120 in a circumferential direction. The slit 120 is formed by cutting the skirt 113 along the axis of the main valve 20, and forms a flow passage area-variable refrigerant passage of the main valve 20, the opening area of which is changed according to the lift amount.

The valve element 112 of the main valve 20 is configured such that the opening width of the slit 120 is reduced as it is closer to the tapered portion 119. With this configuration, when the valve element 112 starts to open from the fully-closed state in which it is seated on the valve seat 27, it is possible to modify the rate of change in the opening area with respect to the amount of motion of the valve element 112. Therefore, in this control valve 111, as shown in FIG. 12, the change in the flow rate relative to electric current supplied to the solenoid is not linear, when the valve seat 27 is positioned in a region where the opening width of the slit 120 is changing after the valve element 112 has started to be lifted, an increase in the flow rate responsive to an increase in electric current is small, and the change in the flow rate relative to the electric current is proportional when the valve element 27 is positioned in a region where the opening width of the slit 120 is constant.

Although described in detail based on the preferred embodiments heretofore, the present invention is by no means limited to the specific forms thereof. For example, in the illustrated examples, the control valve is disposed in a discharge-side refrigerant passage of the variable displacement compressor to control the flow rate of refrigerant introduced into the crankcase 1, this is not limitative, but the control valve may be disposed in a suction-side refrigerant passage, and the main valve senses the flow rate of refrigerant flowing through the suction-side refrigerant passage, to control the flow rate of refrigerant flowing from the crankcase 1 out into the suction chamber.

The control valve for a variable displacement compressor, according to the present invention, comprises the main valve and the solenoid valve having a valve portion which is commonly used as part of the main valve. Therefore, the control valve is advantageous in that it can be realized by a very simple construction, and a stable flow rate control is possible since the solenoid valve performs actuation control of the valve portion smaller than the main valve.

Further, in the variable displacement compressor, there occurs a large differential pressure between during operation and during stoppage of operation, and when the compressor is changed from an operating state into an operation stoppage state, pressure corresponding to the differential pressure is returned to the discharge chamber at a dash. To prevent this, a check valve is disposed at an outlet port of the compressor. In the control valve according to the present invention, the main valve is formed by a check valve structure in which it is lifted by the flow rate of refrigerant flowing in one direction. This is advantageous in that it is possible to dispense with the check valve disposed at the outlet port, and thereby reduce the cost of the compressor.

The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents. 

1. A control valve for a variable displacement compressor, for providing control such that a flow rate of refrigerant discharged from the compressor becomes constant, comprising: a main valve that is set to a first valve lift a lift amount of which is dependent on a flow rate of refrigerant passing therethrough which is discharged from a discharge chamber of the compressor; and a solenoid valve that is set to a second valve lift by an external signal, and controls a flow rate of refrigerant to be allowed to flow from the discharge chamber to a crankcase according to an amount of change in the first valve lift relative to the second valve lift set thereto.
 2. A control valve for a variable displacement compressor, for providing control such that a flow rate of refrigerant discharged from the compressor becomes constant, comprising: a main valve that has a valve seat formed in a refrigerant passage communicating between a first port to be connected to a discharge chamber of the compressor and a second port to be connected to an outlet port of the compressor, and a valve element that is disposed at a location downstream of the valve seat, in a state urged in a valve-closing direction such that the valve element can be moved to and away from the valve seat; and a solenoid valve that is disposed coaxially with the main valve, and has a hollow cylindrical body having a hollow portion, one open end opening in the first port, and another open end opening in a third port to be connected to a crankcase of the compressor, the hollow cylindrical body being urged along a same axis as that of the main valve, the valve element of the main valve being regarded as a movable valve seat or a movable valve element and forming a valve portion in cooperation with the hollow cylindrical body.
 3. The control valve according to claim 2, wherein the valve element of the main valve is configured such that the valve element has an axially extending piston inserted in a through hole axially formed therethrough, and is movable axially back and forth using the piston as a guide, the valve portion of the solenoid valve being a slide valve configured such that the one end of the hollow cylindrical body is disposed in a manner removably insertable into the through hole.
 4. The control valve according to claim 2, wherein the valve element of the main valve is configured such that a hollow cylindrical valve element having a same diameter as the hollow cylindrical body is fitted in a through hole axially formed through the valve element, and the hollow cylindrical valve element is held in an axially recessed guide in a manner movable axially back and forth, whereby the valve element of the main valve is movable axially back and forth, the valve portion of the solenoid valve comprising a hollow cylindrical movable valve seat having a funnel-like shape formed by expanding the one open end of the hollow cylindrical body opening in the first port, and the hollow cylindrical valve element fitted on the valve element of the main valve.
 5. The control valve according to claim 2, wherein the valve element of the main valve is configured such that the valve element has an axially extending piston inserted in a through hole axially formed therethrough, and is movable axially back and forth using the piston as a guide, the valve portion of the solenoid valve being a poppet valve configured such that a frustoconical valve element having a frustoconical shape at one end of the hollow cylindrical body is disposed such that the frustoconical valve element can be moved to and away from a rim of the through hole.
 6. The control valve according to claim 2, wherein the valve element of the main valve comprises a hollow cylindrical skirt slidably disposed in a valve hole of the main valve and having a slit forming a passage in the main valve, and a hollow cylindrical portion forming a valve seat of the solenoid valve, the skirt and the hollow cylindrical portion being coaxially arranged and formed integrally with each other, the valve portion of the solenoid valve being a poppet valve configured such that a frustoconical portion formed at one end of the hollow cylindrical body is disposed such that the frustoconical portion can be moved to and away from the hollow cylindrical portion.
 7. The control valve according to claim 6, wherein the slit formed in the skirt is varied in opening width thereof in a direction in which the valve element of the main valve is lifted.
 8. The control valve according to claim 2, wherein the hollow cylindrical body has closed opposite ends and a side provided with holes opening into the first port and the third port, and wherein the valve element of the main valve is configured such that the valve element has the hollow cylindrical body inserted in a through hole axially formed therethrough, and is movable axially back and forth using the hollow cylindrical body as a guide, the valve portion of the solenoid valve being a slide valve formed by the open end opening into the first port and the valve element of the main valve.
 9. The control valve according to claim 2, wherein the hollow cylindrical body is held by a body accommodating the main valve and the solenoid valve or by a core of the solenoid provided in the body, in a manner movable axially back and forth, an end of the hollow cylindrical body on a side opposite from the main valve being fixed to a plunger of the solenoid.
 10. The control valve according to claim 2, wherein the hollow cylindrical body is held by a body accommodating the main body and the solenoid valve or by a core of the solenoid provided in the body, in a manner movable axially back and forth, an end of the hollow cylindrical body on a side opposite from the main valve being in abutment with a shaft fixed to a plunger of the solenoid.
 11. The control valve according to claim 2, wherein the main valve includes damper means for suppressing a sudden motion of the valve element responsive to a sudden change in pressure of refrigerant supplied from the discharge chamber. 